As a result of an excessive intake of fats due to changes of diet, changes in environment, increase in the exposure to ultraviolet rays due to destruction of the ozone layer, increases in environment pollutants and the like, the number of patients with so-called lifestyle-related diseases such as hyperlipemia, hypercholesterolemia, hypertension, diabetes and cancers is increasing and also the number of patients with allergy or brain diseases such as dementia is increasing. With a progress in aging of society, an increase in the number of patients with dementia, Alzheimer's syndrome, and the like in future is feared; it has been pointed out that active oxygen species generated in the organism are involved in these diseases (Bioorganic & Medicinal Chemistry, 10 (2002), 2497-2509). However, since no technology that completely suppresses or controls generation of active oxygen species has been developed yet, there are no established technologies which are sufficiently effective and reliable for preventing or treating lifestyle-related diseases, brain diseases, and the like at present.
In recent years, attention has been focused on natural substances that are found in plants and exhibit physiological activities, particularly polyphenol compounds. Polyphenols are generally contained in tea, vegetables, fruits, herbs, and the like and are expected to be useful as treating or preventive agents having no side effect, which has been confirmed from a long-term intake as a food or favorite.
Polyphenol compounds are secondary metabolites of plants and known to universally and abundantly occur in the plant world and exhibit various physiological activities. Polyphenol compounds have received attention in the field of pharmacology, plant chemistry, and the like since long ago, and are recently attracting attention from the filed of health food. For example, it is known that polyphenols in tea, particularly catechins, exhibit a wide variety of physiological activities such as antimicrobial effect, antiviral effect, antimutational effect, antioxidative effect, effect for preventing pressure increase, effect for lowering blood cholesterol, anticarious effect, antiallergic effect, effect for improving intestinal flora and deodorant effect.
Among polyphenols, proanthocyanidins are polyphenols that are contained in a wide variety of plants. In order for proanthocyanidins to exhibit various physiological activities as mentioned above, proanthocyanidin compounds have to be absorbed in an organism through intestine. However, proanthocyanidins are said to have molecular weights generally on the order of several thousands to several ten thousands. Substance having such a high molecular weight is difficult to be absorbed through the intestine. Even when the proanthocyanidins are taken in, in most cases, they are not absorbed into the living body, so that they are not utilized by the living organism.
The inventors of the present invention have found that a polyphenol extracted from buckwheat has activities of improving lipid metabolism, brain function, and so on and filed a patent application (JP 10-218786 A) based on the findings. The active ingredient of the polyphenol is a proanthocyanidin polymer, and its bioabsorbability has been considered as less than sufficient.